sudden burst of realization

call me silly but i just found out that "you are my sunshine" is a very sad song.

You are my sunshine
My only sunshine
You make me happy
When skies are gray
you never know dear
How much i love you
Please don't take
My sunshine away...

tell me how can that not be sad? i mean how the persona practically begged for the sunshine to not to go away. worst thing is it is his/her ONLY sunshine. honestly i cried when i heard it... and it played in my head time and time again...

deep in my heart i beg to GOD
please don't take MY sunshine away...
i can't live without it,
my whole world be dark and gloomy,
i will be lost,
please oh please don't take away my sunshine...
i really really need it...